淨名經集解關中疏 2.30

2.30

又問。空何用空　生曰。若理果是空。何用空惠然後空。肇曰。上空法空。下空智空也。諸法本性自空。何假智空然後空耶。

"He also asked: 'How does emptiness use emptiness?'"—Daosheng says: "If the principle is indeed empty, why use the wisdom of emptiness only after which it is empty?" Sengzhao says: "The upper 'emptiness' is emptiness of dharmas; the lower 'emptiness' is emptiness of wisdom. The fundamental nature of all dharmas is of itself empty; why rely on the emptiness of wisdom only after which they are empty?"